Servo mechanism



E. P. RENAUX SERVO MECHANISM Jan. 5, 1932.

Original Filed March 14, 1923 INVENTOR E uargyE F. RENAUX 4J7 ATTORNEY Patented Jan. 5, 1932 UNITED STATES PATENT EUGENE PROSPER RENAUX, OF PARIS, FRANCE, ASSIGNOR TO BENDIX COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS SERVO MECHANISM Original application filed March 14, 1923, Serial No. 625,072, and in France December 14, 1922. Divided and this application filed April 15, 1926. Serial No 102,137.

This invention relates to brakes and is illustrated as embodied in an internal expanding brake for an automobile wheel.

An object of the invention is to provide novel power-multiplying connections operated by a servo shoe for applying the friction means of the brake. In one desirable arrangement, a cam or the like which operates the friction means, such as an anchored brake shoe, is rocked by a lever expanding radially inward of' the drum from a fulcrum adjacent the circumference of the drum, the lever being connected by a link to a servo shoe which turns with the drum to apply the brake. Other features of novelty relate to a guide for the servo shoe shown as a stationary member projecting in the slot at the end of the shoe, and to the general arrangement of the shoes and power-multiplying connections, all of which will be apparent from the following description of one illustrative embodiment of the invention shown in the accompanying drawing, in which:

The figure is a vertical section through the brake just inside the head of the brake drum and showing the brake shoes in side elevation.

The particular brake selected for illustration includes a rotatable drum 10 having the usual cylindrical peripheral braking flange, within which is arranged the friction means of the brake shown as including an arcuate and substantially rigid brake shoe 12 anchored by being mounted on a pivot 14 carried by a backing plate or other stationary support 16 at the open side of the brake drum. This brake shoe is forced against the drum against the resistance of the return spring 18 connected at its ends to the shoe and to the backing plate by means such as a double cam 20 engaging a wear plate 22 on the end of the shoe and mounted on a shaft or spindle 24 carried by the backing plate 16 and rocked in applying the brake by a lever 26 fulcrumed on the spindle and extending radially inward with respect to the drum. The lever 26 is rocked by a servo shoe 28 through the medium of a link 30 pivoted at its ends to the inner end of the lever and to one end of the servo shoe. -A servo shoe of this type is sometimes referred to as a booster or relay shoe.

According to an important minor feature of the invention the servo shoe 28 is formed with a guide slot 32 which is co-axial with respect to the drum when the drum is applied and into which there projects a pin or other part 34 carried by the backing plate 16. The servo shoe is forced against the drum in applying the brake by means such as a roller 36 on a crank arm 38 operated by a shaft 40 connected to the usual brake-operating con-- nections, against the resistance of the return spring 42 connected at its end to the backing plate 16.

In operation when the shoe 28 is forced against the drum it will turn with the drum a short distance one way or the other, according to the direction the drum is turning, to rock the lever 26 so that one end or the other of the double cam 20 will force shoe 12 against the drum.

While one illustrative embodiment of the invention has been described in detail, it is not my intention to limit its scope to that particular embodiment or otherwise than by the terms of the appended claims. Most of the subject-matter herein claimed is to be regarded as divided from my prior application No. 625,072, filed March 14, 1923.

I claim:

1. A brake comprising, in combination, a rotatable drum, an anchored shoe within the drum, a lever fulcrumed adjacent the cir eumference of the drum and extending radially inward and having means for forcing the anchored shoe against the drum, a servo shoe arranged end to end with respect to the anchored shoe, a link pivotally connected at its ends tothe end of the lever and to the servo shoe and means for applying force radially to the servo shoe.

2. A. brake comprising, in combination, a rotatable drum, a support adjacent the drum, an anchored shoe and a servo shoe arranged end to end and engageable with the same zone of the surface of the drum, the servo shoe being formed adjacent one end with a slot curved about the axis of the drum, a projec tion on the support extending into the slot to j guide the servo shoe, and means operated by the servo shoe for forcing the anchored shoe against the drum.

3. A brake comprising, in combination, a support provided with a pin, a floating servo shoe associated with said support'and provided with an arcuate slot Within which said pin is adapted to extend.

4. A brake comprising in combination a rotatable drum, a support adjacent the open face of the drum, a brake shoe anchored at one end within the drum, a servo shoe positioned within the drum and adapted to engage the same zone as the said brake shoe, a pin and slot guiding connection between the servo shoe and the support and applying means connecting the servo and said anchored shoe.

5. A brake comprising in combination a rotatable drum, a support adjacent the drum, an anchored shoe and an unanchored shoe mounted within the drum and arranged end to end, a pin and slot guiding connection between the servo shoe and a support and power-multiplying applying means connecting the servo and the anchored shoes.

6. A brake comprising a drum, a support, an anchored friction shoe and an unanchored servo shoe arranged end to end within the drum, the servo shoe being formed with a substantially circumferential slot, a pin secured to the support and received in the slot, and power multiplying means connecting the servo and anchored shoes.

7. A brake comprising a drum, a support, an anchored friction shoe and an unanchored servo shoe arranged end to end within the drum, the servo shoe being formed with a substantially circumferential slot, a pin secured to the support and received in the slot, and power multiplying means extending between the anchored and the servo shoes and con-V nected to the servo shoe adjacent said slot.

8. A brake comprising a drum, a backing plate positioned adjacent the open face of the drum, an anchored shoe and an unanchored servo shoe positioned end to end within the drum, means on the backing plate to move the servo shoe radially for drum engagement and power applying means connecting the servo and anchored shoes.

9. A brake comprising a drum, a backing plate positioned adjacent the open face of the drum, an anchored shoe and an unanchored servo shoe positioned end to end within the drum, means on the backing plate to move the servo shoe radially against the drum for circumferential movement and power applying means connecting the servo and anchored shoes including a lever fulcrumed adjacent the circumferenceof the drum and having a power arm positioned radially inwardly of the drum.

In testimony whereof, I have hereunto signed my name.

EUGENE PROSPER RENAUX. 

